Secondary battery

Abstract

The present invention relates to a secondary battery which is capable of improving safety. As an example, a secondary battery which comprises an electrode assembly; a case which accommodates the electrode assembly; a cap assembly which is coupled to an upper portion of the case, and a gasket which is interposed between the cap assembly and the case, wherein the cap assembly comprises a cap-up, a safety vent which is installed at a lower portion of the cap-up, a cap-down which is installed at a lower portion of the safety vent, an insulator which is interposed between the safety vent and the cap-down, and a sub-plate which is located on a lower surface of the cap-down, and an insulation layer is formed on one surface of the safety vent, is disclosed.

The invention claimed is: 
     
       1. A secondary battery comprising:
 an electrode assembly; 
 a case accommodating the electrode assembly; 
 a cap assembly coupled to an upper portion of the case, and comprising:
 a cap-up; 
 a safety vent at a lower portion of the cap-up; 
 a cap-down at a lower portion of the safety vent; 
 an insulator between the safety vent and the cap-down, and contacting one surface of the safety vent; and 
 a sub-plate on a lower surface of the cap-down, 
 
 a gasket between the cap assembly and the case; and 
 an insulation layer contacting inner and outer peripheral surfaces of the insulator, and contacting the one surface of the safety vent 
 wherein the insulation layer defines a gap or hole therein at a portion of the safety vent at which the insulator contacts the safety vent. 
 
     
     
       2. The secondary battery of  claim 1 , wherein the insulation layer comprises an anodized surface on the safety vent wherein the insulation layer defines a gap or hole therein at a portion of the safety vent at which the insulator contacts the safety vent. 
     
     
       3. The secondary battery of  claim 2 , wherein the insulation layer comprises aluminum oxide. 
     
     
       4. The secondary battery of  claim 1 , wherein edges of the safety vent upwardly extend to an upper portion of the cap-up to encompass edges of the cap-up. 
     
     
       5. The secondary battery of  claim 1 , wherein the safety vent comprises a first surface contacting the cap-up, and a second surface opposite to the first surface, and
 wherein the insulation layer is formed on the second surface. 
 
     
     
       6. The secondary battery of  claim 1 , wherein the insulation layer is between the safety vent and the gasket. 
     
     
       7. The secondary battery of  claim 1 , further comprising a protrusion part that downwardly protrudes at a center of the safety vent, and that is electrically connected to the sub-plate. 
     
     
       8. The secondary battery of  claim 1 , wherein the insulation layer insulates the safety vent and the case from each other. 
     
     
       9. The secondary battery of  claim 1 , wherein the electrode assembly comprises a first electrode, a second electrode, and a separator between the first electrode and the second electrode,
 wherein the safety vent is electrically connected to the first electrode through the sub-plate, and 
 wherein the case is electrically connected to the second electrode.